A man has revealed how a cancer patient thousands of miles away benefited from him donating his stem cells.
Sam Schmidt, 25, from London, signed up to the stem cell donor register after a blood-cancer patient gave an inspirational talk at his workplace in 2019.
Around a year later, the press officer was told he was a "perfect match" for a different cancer patient in Canada.
In May 2020, Schmidt spent a day in hospital, having his stem cells collected while "watching Netflix".
Schmidt has since been told his stem cells "really helped", with the cancer patient then able to come off certain treatments.
This comes amid news the number of people joining the register has halved during the pandemic.
Around a quarter of a million people are living with blood cancer in the UK alone, with one in 16 men and one in 22 women developing the disease at some point in their life.
"For many patients, their only chance of survival is to find a matching blood stem-cell donor, as fast as possible," according to DKMS, "an international nonprofit organisation dedicated to the fight against blood cancer and blood disorders".
Less than a third (30%) of blood-cancer patients have a compatible donor in their family.
All blood cells originate from stem cells. Known as "mother cells", these do not have a specific function. They instead renew and differentiate into more specialised cells in bone marrow, before entering the bloodstream.
In blood-cancer patients, this process is obstructed, leading to immature or abnormal blood cells entering the bloodstream and multiplying uncontrollably into tumours.
These cancer cells then flood the bloodstream, driving out healthy cells. As a result, the blood cannot perform its basic tasks, like transporting oxygen around the body.
Stem-cell transplants aim to right this process.
After hearing the inspirational talk, Schmidt signed up to the stem cell donor register, with his cheek being swabbed for laboratory analysis.
A year later, when the swab was a "brief memory", Schmidt was told he may be a "perfect match" for a male blood-cancer patient, which was later confirmed by a blood test.
"I got a bit nervous, thinking 'I hope my stem cells are good enough'," Schmidt told Yahoo UK. "You feel a bit of responsibility."
Amid the pandemic, Schmidt was taught how to self-inject with a substance that stimulated his stem cells, something done by a nurse in normal circumstances.
"Four days prior [to the stem cells being collected], I had to do it two times a day," said Schmidt.
"I was quite nervous as I'd never injected myself before but it was so smooth and painless. The only side effect I got was a slightly sore back."
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Schmidt's stem cells were later collected via apheresis, as is the case in nine in 10 (90%) incidences.
"They laid me in bed and connected my left arm into the machine," he said.
"A centrifuge then separates the different parts [of the blood] and runs the blood back into your right arm.
"It was quite a pleasant experience. I got the day off work, and got to lie down and watch Netflix for four or five hours."
In one in 10 (10%) cases, stem cells are collected from the back of the donor's pelvic bone under general anaesthetic.
"Whether the cells are removed from your bloodstream or bone marrow ultimately depends on what's best for the patient and what their treating physician decides after careful consideration," according to DKMS.
The apheresis was "not at all" painful, with Schmidt feeling "perfectly relaxed" throughout.
"It's really not very taxing at all," he said.
Regardless of where in the world a person's stem cells are sent, "there is at least a two-year period of anonymity" between the donor and recipient.
Nevertheless, Schmidt has been told his donation "really helped".
"They [medics] told me they'd stopped certain radioactive treatments [on the patient as a result of him receiving the stem cells]," said Schmidt.
In October 2020, Schmidt went back to hospital to provide a "small top-up" of his plasma – the liquid part of blood – for the patient.
Amid the pandemic, Schmidt's stem cells were frozen and flown to Canada.
"I don't know if in normal circumstances he'd have been flown over," said Schmidt.
"I have no ties to Canada at all. It just shows you can be a match for anyone all over the world."
Young male donors "produce more stem cells", leading to a greater chance of transplant success.
While seven in 10 (70%) stem-cell transplants are donated by men, just four in 10 (40%) donors worldwide are male. Young males specifically, aged 18 to 30, make up just 7% of registered donors in the UK.
"I'm amazed more people aren’t signed up," said Schmidt.
"People who are so unfortunate to have such a horrible disease could actually have a chance [if you sign up to the register].
"What if your own brother/mother/father/son had it [blood cancer]?
"You'd want the same for your family."
This World Blood Cancer Day, DKMS is encouraging people to show solidarity for blood-cancer patients by uploading a selfie with the #WearItRed hashtag.
"By registering as a potential blood stem-cell donor, you could save the life of a stranger in need," the charity has said.
"If you're 17-55 (and in general good health) request a home swab kit today."
Watch: Four-month-old needs stem-cell transplant